<template>
  <div class="pagination">
    <button :disabled="pageNo == 1" @click="$emit('getPageNo', pageNo - 1)">
      上一页
    </button>
    <button
      v-if="startNumAndEndNum.start > 1"
      @click="$emit('getPageNo', 1)"
      :class="{ active: pageNo == 1 }"
    >
      1
    </button>
    <button v-if="startNumAndEndNum.start > 2">···</button>
    <!-- 中间部分 -->
    <button
      v-for="(page, index) in startNumAndEndNum.end"
      :key="index"
      v-if="page >= startNumAndEndNum.start"
      @click="$emit('getPageNo', page)"
      :class="{ active: pageNo == page }"
    >
      {{ page }}
    </button>
    <button v-if="startNumAndEndNum.end < totalPage - 1">···</button>
    <button
      v-if="startNumAndEndNum.end < totalPage"
      @click="$emit('getPageNo', totalPage)"
      :class="{ active: pageNo == totalPage }"
    >
      {{ totalPage }}
    </button>
    <button
      :disabled="pageNo == totalPage"
      @click="$emit('getPageNo', pageNo + 1)"
    >
      下一页
    </button>

    <button style="margin-left: 30px">共 {{ total }} 条</button>
  </div>
</template>

<script>
export default {
  name: "Pagination",
  // pageNo：当前第几页
  // pageSize：代表一页展示多少条数据
  // total：代表整个分页总共多少条数据
  // continues：代表分页连续页码的个数
  props: ["pageNo", "pageSize", "total", "continues"],
  computed: {
    totalPage() {
      // 总共有多少页 Math.ceil向上取整
      return Math.ceil(this.total / this.pageSize);
    },
    startNumAndEndNum() {
      const { continues, pageNo, totalPage } = this; // 解构
      let start, end;
      // 不正常现象【总页数没有连续页码多】
      if (continues > totalPage) {
        start = 1;
        end = totalPage;
      } else {
        // 正常现象【连续页码5，总页数是大于5的】
        start = pageNo - Math.floor(continues / 2);
        end = pageNo + Math.floor(continues / 2);
        if (start < 1) {
          start = 1;
          end = continues;
        }
        if (end > totalPage) {
          start = totalPage - continues + 1;
          end = totalPage;
        }
      }
      return { start, end };
    },
  },
};
</script>

<style scoped>
.pagination {
  text-align: center;
}
.pagination button {
  margin: 0 5px;
  background-color: #f4f4f5;
  color: #606266;
  outline: none;
  border-radius: 2px;
  padding: 0 4px;
  vertical-align: top;
  display: inline-block;
  font-size: 13px;
  min-width: 35.5px;
  height: 28px;
  line-height: 28px;
  cursor: pointer;
  box-sizing: border-box;
  text-align: center;
  border: 0;
}
.pagination .active {
  background: skyblue;
}
</style>
